(1) Field of the Invention
The present invention pertains to a pneumatically controlled apparatus for automatically disconnecting a trailer from a supporting bogie in a tractor-trailer rig.
(2) Description of the Related Art
Tractor-trailer rigs comprising truck trailers supported by bogies in a manner that enables a sliding adjustment of the positions of the trailers on the bogies are well known in the prior art. In general, this type of trailer rig is comprised of a truck trailer having a pair of spaced, parallel rails extending longitudinally beneath the bed of the trailer. The truck bogie is positioned between the pair of rails and is connected to the rails in such a way that the position of the bogie beneath the trailer is adjustable by sliding the bogie fore and aft relative to the trailer The bogie is adjusted relative to the trailer it supports in order to adjust the load carried by the trailer on the bogie. Additionally, a typical bogie is often adjusted forward relative to the trailer it supports to facilitate cornering with the adjusted tractor-trailer rig.
A bogie is typically constructed with a frame supporting the wheels and suspension systems of the bogie, the wheel brakes, and a pneumatic pressure reservoir tank and pneumatic pressure conduits. The conduits provide fluid communication between a source of pneumatic pressure on the tractor and the reservoir tank and wheel brakes of the bogie, and between the brakes and the brake controls in the tractor pulling the trailer and bogie assembly. The pneumatic conduits typically include a service conduit system for conducting the supply of pneumatic pressure to the service wheel brakes, enabling selective engagement of the brakes during driving operations of the tractor-trailer rig. The typical bogie also comprises a second, emergency or parking brake pneumatic conduit system that controls the emergency brakes of the bogie. The emergency brake system controls the emergency brakes to engage when pneumatic pressure is drained from the emergency brake system, and to disengage when pneumatic pressure is supplied to the emergency brake system. The emergency brake system is always disengaged when the tractor-trailer rig is operated over the road.
In most truck trailer and bogie assemblies, the spaced longitudinal rails of the trailer are provided with a series of holes along a portion of their lengths. The bogie is provided with four pins that engage in four of the rail holes to secure the bogie in an adjusted position relative to the trailer. By retracting the pins out of the rail holes, the bogie is free to be adjusted fore and aft relative to the trailer rails to position the bogie in an optimum position beneath the trailer for a desired turning radius of the tractor-trailer rig or a desired distribution of load on the bogie wheels.
A manually operated mechanical linkage system is provided on the bogie frame for retracting the four pins from the holes in the trailer rails. Prior to retracting the pins, the tractor-trailer rig operator first sets the emergency brakes of the truck trailer and bogie assembly. A manual handle of the linkage mechanism near the forward end of the bogie is then manipulated by the rig operator, causing the four pins to be retracted from the trailer rail holes and locking the pins in their retracted positions. With the pins retracted and the bogie emergency brakes engaged, the trailer is free to slide over the bogie. The tractor-trailer rig operator then drives the tractor either forward or backward to adjust the position of the trailer on the bogie either forward or backward, respectively. Once the trailer has been moved over the bogie to its desired position relative to the bogie, the operator then exits the tractor and releases the manual handle of the linkage mechanism, causing a spring bias of the linkage mechanism to reinsert the four pins into holes of the trailer rails and thereby securing the bogie in its adjusted position beneath the trailer.
Use of the prior art pin retracting linkage mechanism has certain disadvantages. Very often, after prolonged periods of use of the truck trailer and bogie assembly, the trailer rails and bogie pins become worn and corroded. This often causes the bogie pins to become jammed in the trailer rail holes, making disconnection of the bogie from the trailer difficult.
A further disadvantage of the prior art pin releasing mechanism is often encountered when the mechanism is operated. The manual handle of the mechanism is frequently positioned just in front of the forward, left wheels of the bogie. To release and engage the mechanism, a person must stand directly in front of the forward, left bogie wheels to manipulate the handle of the mechanism. This exposes the person to considerable danger should the emergency brakes of the tractor-trailer rig slip while attempting to retract or reengage the bogie pins into the rail holes of the trailer.
What is needed to overcome these disadvantages associated with the prior art bogie pin retracting mechanism is a power actuated system for retracting the pins, such as a system that automatically operates under the existing pneumatic pressure of the tractor-trailer rig. Such a system would provide an increased force for disengaging stuck bogie pins from the rail holes of a truck trailer, and would also provide automatic operation that does not require a person to stand in front of the forward, left bogie wheels when operating the device as is necessary when operating the prior art mechanism.